Analysis
of children and young people's proximity to woodlands has shown links
with better cognitive development and a lower risk of emotional and
behavioral problems, in research led by UCL and Imperial College London
scientists that could influence planning decisions in urban areas.
In
what is believed to be one of the largest studies of its kind,
researchers used longitudinal data relating to 3,568 children and
teenagers, aged nine to 15 years, from 31 schools across London. This
period is a key time in the development of adolescents' thinking, reasoning and understanding of the world.
The study, published in Nature Sustainability, looked at the links between different types of natural urban environments and the pupils' cognitive development, mental health and overall well-being.
The environments were divided into what planners call green space (woods,
meadows and parks) and blue space (rivers, lakes and the sea), with
green space separated further into grassland and woodland. Researchers
used satellite data to help calculate each adolescent's daily exposure
rate to each of these environments within 50m, 100m, 250m and 500m of
their home and school.
After
adjusting for other variables, the results showed that higher daily
exposure to woodland (but not grassland) was associated with higher
scores for cognitive development, and a 16% lower risk of emotional and
behavioral problems two years later.
A
similar but smaller effect was seen for green space, with higher scores
for cognitive development, but this was not seen for blue space. The
researchers note though that access to blue space in the cohort studied
was generally low.
Examples
of other explanatory variables considered included the young person's
age, ethnic background, gender, parental occupation and type of school,
e.g., state or independent. The level of air pollution might have
influenced adolescents' cognitive development, but researchers did not
feel these observations were reliable or conclusive, and these require
further investigations.
It
is already estimated that one in 10 of London's children and
adolescents between the ages of five and 16 suffer from a clinical
mental health illness and excess costs are estimated between £11,030 and
£59,130 annually for each person. As with adults, there is also
evidence that natural environments play an important role in children
and adolescents' cognitive development and mental health into adulthood,
but less is known about why this is.
The
results of this study suggest that urban planning decisions to optimize
ecosystem benefits linked to cognitive development and mental health
should carefully consider the type of natural environment included.
Natural environments further away from an adolescent's residence and
school may play an important role too, not just their immediate
environment.
Lead
author, Ph.D. student Mikaël Maes (UCL Geography, UCL Biosciences and
Imperial College London School of Public Health) said: "Previous studies
have revealed positive associations between exposure to nature in urban
environments, cognitive development and mental health. Why these health
benefits are received remains unclear, especially in adolescents.
"These
findings contribute to our understanding of natural environment types
as an important protective factor for an adolescent's cognitive
development and mental health and suggest that not every environment
type may contribute equally to these health benefits.
"Forest
bathing, for example (being immersed in the sights, sounds and smells
of a forest), is a relaxation therapy that has been associated with
physiological benefits, supporting the human immune function, reducing
heart rate variability and salivary cortisol, and various psychological
benefits. However, the reasons why we experience these psychological
benefits from woodland remain unknown."
Joint
senior author Professor Mireille Toledano (Director, Mohn Centre for
Children's Health and Wellbeing and Investigator, MRC Centre for
Environment and Health and Principal Investigator of the SCAMP study,
Imperial College London) said: "It's been suggested previously that the
benefits of natural environments to mental health are comparable in
magnitude to family history, parental age and even more significant than
factors like the degree of urbanization around you, but lower than your
parents' socio-economic status. Sensory and non-sensory pathways have
been suggested as potentially important for delivering cognition and
mental health benefits received from exposure to nature.
"It's
critical for us to tease out why natural environments are so important
to our mental health throughout the life course—does the benefit derive
from the physical exercise we do in these environments, from the social
interactions we often have in them, or from the fauna and flora we get
to enjoy in these environments or a combination of all of these?"
Joint
senior author Professor Kate Jones (UCL Centre for Biodiversity &
Environment Research, UCL Biosciences) said: "One possible explanation
for our findings may be that audio-visual exposure through vegetation
and animal abundance provides psychological benefits, of which both
features are expected in higher abundance in woodland. Even though our
results show that urban woodland is associated with adolescent's
cognitive development and mental health, the cause of this association
remains unknown. Further research is fundamental to our understanding of
the links between nature and health."
To
arrive at the findings, researchers analyzed a longitudinal dataset of
3,568 adolescents between 2014 and 2018, whose residence was known, from
the Study of Cognition, Adolescents and Mobile Phones (SCAMP) across
the London metropolitan area. They assessed adolescents' mental health and
overall well-being from a self-reported Strengths and Difficulties
Questionnaire (SDQ) - covering areas such as emotional problems,
conduct, hyperactivity and peer problems—and the KIDSCREEN-10
Questionnaire taken by each adolescent for SCAMP.
Limitations of the study include an assumption that living or going to school near natural environments means
more exposure to them, which may not always be the case due to how
easily they can be accessed by a child or young person or how usable
they are.
Also,
a considerable proportion of the participants (52.21%) were in the
group whose parents had a managerial/professional occupation, so
adolescents in less favorable socio-economic groups may be
underrepresented and pupils requiring special needs may be differently
affected compared with their peers. Crime rates, which may have
influenced the results too, were not taken into account.